This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Sperm are remarkable cells specialized for the delivery of the paternal genome to the oocyte, while embryos consist of rapidly dividing, largely undifferentiated cells. Unlike embryos, sperm have jettisoned most cellular components, have highly compacted chromatin, and are thought to be largely transcriptionally inactive. Thus, sperm rely on substitution histones and post-translational modification (PTM) of existing proteins for development and function. In other organisms, replacement of S-phase histones by histone variants and protamines fundamentally changes chromosome architecture at the nucleosome level. How chromatin differs between these two tissue types has been largely unexplored. To investigate the nature of C. elegans sperm chromatin composition, we conducted a global analysis of sperm and embryo chromatin proteins using Multidimensional Protein Identification Technology (MudPIT) mass spectroscopy. Our novel approach to determine chromatin composition between disparate cell types has identified over 1000 proteins from embryos and sperm each, laying the groundwork for analysis of other histone subtypes as well as protamine orthologs. In addition, our ongoing large-scale identification of histone PTMs is a valuable resource to examine how paternal epigenetic marks contribute to embryonic development.